1. Field of the Invention
This invention relates to a driving apparatus in a camera, and more particularly to a stop and/or mirror driving apparatus in a single lens reflex camera.
2. Description of the Prior Art
In single lens reflex cameras having an aperture control device of the type in which metering is effected while the aperture of the lens is stopped down and the stop-down is discontinued at a point of time whereat a metering value corresponding to a desired aperture has been reached, either a system whereby the aperture diameter is determined with a reflecting mirror remaining in the object observation position or a system whereby the aperture diameter is determined after the reflecting mirror has been retracted from the phototaking light path is conceivable.
In the former, the light to the metering system may reach a light-receiving element via the reflecting mirror and in the latter, metering may be accomplished by utilization of the reflection of the forward shutter curtain or the like. In the former type, the reflecting mirror must be moved up after the aperture diameter has been determined. Therefore, there is a system designed such that, as shown in Japanese Laid-open Patent Application No. 99731/1975 (a first prior art), the restraint of the reflecting mirror is released after lapse of a predetermined time from the operation of a stop restraining electromagnet, and a system as shown in Japanese Patent Publication No. 17908/1976 (a second prior art) wherein a timer is started by the release operation of the camera and the restraint of the reflecting mirror is released by an electromagnetic device when a sufficient time required for stop-down to be completed has elapsed, and in an example shown in U.S. Pat. No. 4,173,403 (a third prior art), the start of upward movement of the reflecting mirror is delayed by the use of a mechanical delay device.
As regards the first prior art, if the delaying operation is started by an electrical signal commanding the operation of the electromagnet, an electromagnetic device will be required for releasing the restraint of the reflecting mirror and this will lead to complexity and increased cost. Also, if a system is adopted whereby the displacement of the member caused by operation of the electromagnet to start a mechanical delay device, the capacity burden of this electromagnet will be great and this will be great and this will lead to bulkiness of the electromagnet and an increase in consumed electric current and further, the mechanical delay device must always quickly return to its original position so as to become ready for the next operation when the camera is continuously operated, and the mechanism for satisfying this will become complex. These disadvantages also hold true of the second and third prior arts.
Further, in the first prior art, the time from after the camera has been released until the electromagnet is operated differs depending on the set value of the aperture and necessarily, the timing for the start of upward movement of the reflecting mirror and the operation of the shutter fluctuates and thus, the photographer cannot exactly grasp the shutter chance.
On the other hand, in the trend of automation of photography, there is seen a tendency to contain a motor within a camera and seek after compactness and simplification of the camera. If, at such time, the above-described mechanism is intactly used, compactness and simplification of the camera will be greatly hampered. Accordingly, there is a demand for an aperture control device of rational construction which makes the best use of the merit that the motor is contained within the camera.
Furthermore, in an aperture control type single lens reflex camera, there is required an apparatus for resetting the stop restraining device responsive to shutter release operation and operated for aperture control. As a first example of the conventional resetting apparatus, there is one in which the resetting of the restraining device is effected during or after the aperture opening operation of returning the aperture to an open aperture value which takes place after completion of exposure. In this apparatus, a member to restrained by the stop restraining device and a member directly operatively associated with the opening-closing of the stop are separated from each other, thereby enabling the aperture opening operation before the resetting of the stop restraining device. However, these two members are designed to operate as a unit during the aperture control operation and this necessarily leads to an increased number of parts and complication of the mechanism.
As a second example of the conventional resetting apparatus, there is one in which the stop restraining device is reset by a resetting member operatively associated with the completion of exposure, and more particularly with the operation of the rearward shutter blade driving mechanism, whereafter the aperture opening operation is effected.
This does not have the above-noted disadvantages but instead has the following disadvantages. Due partly to the technical advancement that the movement energy has been reduced by the lighter weight of the shutter blade or curtain, the driving energy of the driving mechanism has been made small with a result that if the resetting member is operatively associated with the initial stage of operation of the driving mechanism, shutter movement will become unstable and irregularity of shutter time will be caused. On the other hand, if the resetting member is operatively associated with the vicinity of the termination of operation of the driving mechanism, unsatisfactory closing of the shutter will be liable to occur perticularly in cold northern districts and there will be a tendency that the resetting of the stop restraining device becomes unreliable.